U.S. Army Scientists Develop Quantum Sensor Able to Cover the RF Spectrum

March 25, 2020 by Alessandro Mascellino

U.S. Army scientists have developed a quantum sensor able to cover the entire radio frequency spectrum.

The new device would be able to detect communication signals from 0 to 100 GHz.

Building on previous research from 2018, the quantum receiver would be able to detect communications signals using the properties of Rydberg atoms, super-sensitive and highly excited atoms.


Atoms in a glass vapor cell in the process of being excited with laser beams to Rydberg states
Atoms in a glass vapor cell in the process of being excited with laser beams to Rydberg states. Image used courtesy of US Army


Using Rydberg Atoms Sensors

The group of researchers, led by army scientist David Mayer, calculated the receiver's channel capacity, otherwise referred to as the rate of data transmission, and then achieved the full-spectrum performance experimentally in their lab.

Specifically, the scientists obtained the desired results by firstly calculating the Rydberg sensor's sensitivity using a combination of analytical and semi-classical Floquet models.

Through these models, they then determined optimal sensitivity at arbitrary field frequency.

Meyer’s team then validated the numeric Floquet model via experimental Rydberg sensor measurements in a range between 1 and 20 GHz, and using analytical models, they compared them with two prominent electric field sensor technologies, namely electro-optic crystals and dipole antenna-coupled passive electronics.

The results showed that the Rydberg sensor can reliably detect signals over the entire spectrum, and with higher performance than the other two technologies.


An artist's rendition of Rydberg atoms that detect incoming RF fields.

An artist's rendition of Rydberg atoms that detect incoming RF fields. Image used courtesy of U.S. Army


Advancements for the Military

Combining this level of performance with the fact these receivers are quite small would give soldiers multiple benefits on the battlefield.

"These new sensors can be very small and virtually undetectable, giving soldiers a disruptive advantage," Meyer said, commenting on the research.

The use of precise measuring devices is making a significant impact on DoD (Department of Defense) capabilities. Such as the advancement of electric field sensors and communication receivers. The scientist, who works at the US Army Combat Capabilities Development Command's Army Research Laboratory, said that while Rydberg-atom based sensors have been in the past considered for general electric field sensing applications, the new performance would be a first in the scientific field.

“While Rydberg atoms are known to be broadly sensitive,” he explained, “a quantitative description of the sensitivity over the entire operational range has never been done."


Future Developments

Given the wide spectrum of frequencies sensors using Rydberg atoms can cover, the new devices present several possibilities for military applications.

"Quantum mechanics allows us to know the sensor calibration and ultimate performance to a very high degree, and it's identical for every sensor," Meyer said. "This result is an important step in determining how this system could be used in the field."

Meyer added that these new sensors will become part of the Army Network, an initiative by the US Army focusing on developing next-generation solutions to stay ahead of potential adversaries.

The team led by Mayer said they will continue to develop sensor technologies to continue to improve their sensitivity in order to detect even weaker signals, as well as expanding detection protocols for more complicated waveforms.

The new findings were published in the Journal of Physics B under the title "Assessment of Rydberg atoms for wideband electric field sensing"